hi Kate,
some of the questions depend on the "customer" decision.
is it OK to assign the PSAPCOMP only to "sapdata4"?
how much space is available? what kind of storage do they have? is totally stripped or not? is there "free" space on the other filesystems?
1.How big size should the PSAPCOMP be , let's say 500G?
as I explained to you already, it is expected that applying all compressions you can save 1/2 of the space but you have to test this as it depends on the content of the tables and selectivity of the indexes. Use the oracle package to simulate the savings for the tables you are going to compress.
do you want the scripts interactive (option -c) or not?
The SAP Database Guide: Oracle has all possible options so you only have to check them
brspace -f tscreate -t PSAPCOMP -s 5120 -a yes -i 100 -m 15360 -f sapdata4 -l 2 --> assign to sapdata4
if you want to create a 500 GB, why you limit the maximum size to 15360?